Dairy butter is a common food product in many parts of the world and is made by a traditional process which varies only slightly from country to country. Basically, the process involves agitation of cream derived from milk to cause separation of the butter fat from milk serum and milk solids of a non fat nature. At the separation stage, globules of milk fat agglomerate to form a solid mass which includes reduced moisture--e.g. approximately 16%--and only a small proportion of solids of a non fat nature. The residual constituents of the original body of cream are drained as butter milk.
The solid body of butter may be subjected to further processing or working after separation and certain additives such as salt may be introduced. The resulting product may be stored under refrigeration.
A common use of the resulting product is as a spread, but its characteristics are such that it is not well suited for that use. As indicated above, it is usual to store dairy butter under refrigerated conditions, but it firms and hardens at a temperature below 15 degrees Celsius and has such a low coefficient of heat transfer as to be slow to soften at higher ambient temperatures encountered upon removal from a refrigerator. Deliberate heating creates other problems due to separation of the constituents and an unattractive oily appearance, and for these and other reasons dairy products can be difficult to handle at temperatures above approximately 30 degrees Celsius.
As a result, there has been a long standing need for dairy butter to have better spreading characteristics at refrigeration temperatures.
It has been observed that natural cheese such as cheddar, containing 50% or more milk fat, when comminuted and emulsified with phosphates, citrates or similar salts and heated under agitation to produce so called "processed cheese" (a commonly manufactured product), can be induced to retain a soft spreadable consistency even when maintained at refrigeration temperatures after manufacture. It has been found that this phenomenon is related to the condition of the casein in the cheese to be processed, and the effect of the emulsifying salts on the casein to produce chains of peptised casein molecules resulting in what is referred to as a short body structure.
The manufacturing procedure for the "processed cheese" includes a heating stage, and it has been found to be not possible to process natural dairy butter in the same manner as cheese since the admixture of emulsifying salts with the butter prior to heating results in separation of the components as the fat component inhibits the action of the emulsifier on the casein. Other pre-blended fats such as vegetable fats or oils with casein and other components are equally resistant to processing in a similar manner.
In spite of extensive investigation into the production of a spreadable refrigerated butter, no such process has heretofore been found, and it is an object of the present invention to provide a method of producing such a food product.